Commit 859d069e authored by Peter Zijlstra's avatar Peter Zijlstra
Browse files

lockdep: Prepare for NMI IRQ state tracking 



There is no reason not to always, accurately, track IRQ state.

This change also makes IRQ state tracking ignore lockdep_off().

Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarIngo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20200623083721.155449112@infradead.org
parent 248591f5

kernel/locking/lockdep.c

+42 −4
Original line number Diff line number Diff line
@@ -395,7 +395,7 @@ void lockdep_init_task(struct task_struct *task) 


static __always_inline void lockdep_recursion_finish(void)

{

	if (WARN_ON_ONCE(--current->lockdep_recursion))

	if (WARN_ON_ONCE((--current->lockdep_recursion) & LOCKDEP_RECURSION_MASK))

		current->lockdep_recursion = 0;

}
@@ -3646,7 +3646,16 @@ static void __trace_hardirqs_on_caller(void) 
 */

void lockdep_hardirqs_on_prepare(unsigned long ip)

{

	if (unlikely(!debug_locks || current->lockdep_recursion))

	if (unlikely(!debug_locks))

		return;



	/*

	 * NMIs do not (and cannot) track lock dependencies, nothing to do.

	 */

	if (unlikely(in_nmi()))

		return;



	if (unlikely(current->lockdep_recursion & LOCKDEP_RECURSION_MASK))

		return;



	if (unlikely(current->hardirqs_enabled)) {
@@ -3692,7 +3701,27 @@ void noinstr lockdep_hardirqs_on(unsigned long ip) 
{

	struct task_struct *curr = current;



	if (unlikely(!debug_locks || curr->lockdep_recursion))

	if (unlikely(!debug_locks))

		return;



	/*

	 * NMIs can happen in the middle of local_irq_{en,dis}able() where the

	 * tracking state and hardware state are out of sync.

	 *

	 * NMIs must save lockdep_hardirqs_enabled() to restore IRQ state from,

	 * and not rely on hardware state like normal interrupts.

	 */

	if (unlikely(in_nmi())) {

		/*

		 * Skip:

		 *  - recursion check, because NMI can hit lockdep;

		 *  - hardware state check, because above;

		 *  - chain_key check, see lockdep_hardirqs_on_prepare().

		 */

		goto skip_checks;

	}



	if (unlikely(current->lockdep_recursion & LOCKDEP_RECURSION_MASK))

		return;



	if (curr->hardirqs_enabled) {
@@ -3720,6 +3749,7 @@ void noinstr lockdep_hardirqs_on(unsigned long ip) 
	DEBUG_LOCKS_WARN_ON(current->hardirq_chain_key !=

			    current->curr_chain_key);



skip_checks:

	/* we'll do an OFF -> ON transition: */

	curr->hardirqs_enabled = 1;

	curr->hardirq_enable_ip = ip;
@@ -3735,7 +3765,15 @@ void noinstr lockdep_hardirqs_off(unsigned long ip) 
{

	struct task_struct *curr = current;



	if (unlikely(!debug_locks || curr->lockdep_recursion))

	if (unlikely(!debug_locks))

		return;



	/*

	 * Matching lockdep_hardirqs_on(), allow NMIs in the middle of lockdep;

	 * they will restore the software state. This ensures the software

	 * state is consistent inside NMIs as well.

	 */

	if (unlikely(!in_nmi() && (current->lockdep_recursion & LOCKDEP_RECURSION_MASK)))

		return;



	/*

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